prokaryotes - bacteria see Domain Bacteria Woese et al. 1990
   Domain "Bacteria" Woese et al. 1990
     Phylum "Proteobacteria" Garrity et al. 2005 see Superphylum Proteobacteria Craig et al. 2010
       Class Betaproteobacteria Garrity et al. 2006
         Order Hydrogenophilales Garrity et al. 2006 [monotypic]
           Family Hydrogenophilaceae Garrity et al. 2006
             1 Genus Hydrogenophilus Hayashi et al. 1999
             2 Genus Petrobacter Bonilla Salinas et al. 2004
             3 Genus Tepidiphilus Manaia et al. 2003
             4 Genus Thiobacillus Beijerinck 1904 (Approved Lists 1980)